Method and arrangement in a wireless communication system

ABSTRACT

According to some embodiments of the invention, a method is provided in a radio network node for scheduling data transmission and/or reception. According to the method, the radio network node predicts ( 530 ) at least one autonomous gap occurrence in which user equipments served by the radio network node will use autonomously created gaps for acquiring system information from a neighboring base station and during which the UE is not able to receive data from, and/or transmit data to, the radio network node. Furthermore, the radio network node schedules ( 560 ) a user equipment for data transmission and/or reception in a time period which does not overlap with any predicted autonomous gap occurrence.

TECHNICAL FIELD

The present disclosure relates generally to a method and an arrangementin a network node. In particular, it relates to scheduling of datatransmission and/or reception.

BACKGROUND

Femto base stations, also called home base stations, have attracted muchinterest recently in the wireless industry. The standardization processfor home base stations is ongoing in 3GPP for Universal TerrestrialRadio Access (UTRA), Evolved UMTS Radio Access (E-UTRA) and WorldwideInteroperability for Microwave Access (WiMAX). Furthermore, in both UTRAand E-UTRA, advanced features related to home base stations such asmobility procedures, interference management and control etc are alsobeing introduced. Home base stations are already operational in othertechnologies such as Global System for Mobile communication (GSM) and3GPP2 CDMA technologies (e.g. CDMA2000 1×RTT and High Rate Packet Data,HRPD).

In legacy UTRAN specifications, four classes of base stations (BS) aredefined, namely the wide area BS that serves macro cell deployment, themedium range BS that serves micro cell deployment, the local area BSthat serves pico cell deployment and the home base station serving theprivate localized premises, like a home or an office. In UTRAN, the homeBS is also called a home NodeB (HNB). In E-UTRAN specifications threeclasses of base stations are defined; Wide area BS, local area BS andhome base station. In E-UTRAN the home BS is also called a Home eNodeB(HeNB).

A home base station may also be referred to as a home access point,femto base station, femto access point, home NodeB, or home eNodeB. Someparticular examples of Home Base Stations are UTRAN FDD/TDD home NodeB,E-UTRAN TDD/FDD home eNB (eNodeB), GSM home base station, CDMA20001×home BS, HRPD home BS, or WiMAX home base station. For simplicity andconsistency, we will use the term home base station (HBS) in the rest ofthe disclosure. This term is intended to covers all types of home accesspoints, including but not limited to those mentioned above. It should beunderstood that a home base station may not only deployed in a privateresidence, but also in other public or private premises such as shoppingmalls, office buildings, etc.

Depending on the operator, a Home Base Station may share the carrierwith macro, micro or pico base stations, i.e. non home base stations.This may be referred to as a mixed carrier scenario. Alternatively, theHBS may be assigned a carrier which is used only for the operation ofhome base stations, i.e. a dedicated carrier scenario.

One main difference between a home base station and other base stationclasses is that a Home Base Station is assumed to be owned by a privatesubscriber, who has the liberty to install it at any location. Thus,strict network planning is not possible in case of Home Base Stationdeployment. This is in contrast to other base station classes, which aredeployed by an operator according to well-defined principles. The lackof precise network planning of Home Base Stations and their densedeployment may have the following consequences:

-   -   High interference towards other base stations, including other        home BSs and the surrounding network, e.g. macro base stations.    -   In case of dense Home BS deployment, the UE may detect, measure        and report a large number of cells, which are served by home        base stations but are not required for mobility.

Access to a home base station may be under the control of the operatoror the owner of the home base station. The access control mechanism fora home BS decides if a given user may or may not connect to that homebase station. The selection of the access control mechanism has a largeimpact on the performance of the overall network, mainly due to its rolein the definition of interference. In UTRAN and E-UTRAN, the concept ofa Closed Subscriber Group (CSG) exists. According to the CSG concept,only a subset of users, defined by the owner of the home base station,are allowed to connect to that particular home base station. Becauseaccess to a HBS may be restricted only to certain users, appropriatemobility procedures to prevent unnecessary handovers towards thenon-allowed home base stations are specified for UTRAN as well as forE-UTRAN. This implies that before initiating a handover to a neighborcell, the serving network node may need to know whether the target cellis a CSG cell or not, i.e. whether the target cell is served by a HBSusing the CSG concept.

Currently, network deployments with several layers comprising macro basestations, pico base stations, home base stations etc are gainingpopularity. In certain areas, coverage from macro layer deploymentoverlaps with areas covered by micro, pico or femto network deployments.Such a network or deployment is called a heterogeneous network. Theseheterogeneous network scenarios are expected to become more and morepopular as a direct consequence of the proliferation of pico, femto, andhome eNBs. In such heterogeneous network deployments, mobilitymanagement is becoming an even more challenging task, because it isquite probable that Physical Cell Identities, PCIs, are frequentlyreused. Hence, a serving node in many cases may have to know whether thetarget cell belongs to a macro, pico or home base station etc.

Thus, in a scenario with home base stations, as well as in heterogeneousnetworks, it is beneficial to uniquely determine the identity and/ortype of potential target cells. This requires information which istransmitted in the cell's system information. Hence, the user equipment(UE) is expected to acquire system information from surrounding basestations, such as neighboring HBSs, and report this information to thenetwork. One example of system information that the UE may need toacquire is the Cell Global Identifier (CGI), which is a uniqueidentifier of a cell. The CGI or E-UTRAN CGI (ECGI) acquisition istypically performed by the UE in response to an explicit requestreceived from the serving network node. One example scenario where thismay occur is when the UE performs neighbor cell measurements onpotential target cells for handover, i.e. to support mobility.

As part of the neighbor cell measurement procedure, the UE will send ameasurement report containing neighbor cell measurements such asReference Symbol Received Power (RSRP) and/or Reference Symbol ReceivedQuality (RSRQ) in E-UTRAN, or Common Pilot Channel Received Signal CodePower (CPICH RSCP) and/or Common Pilot channel received energy per chipdivided by power spectral density (CPICH Ec/No) in UTRAN. The servingnetwork node typically uses these measurements to determine if the UEwould be better served by one of the neighbor cells, i.e. whether toinitiate a handover (HO).

The measurement report also comprises the physical cell identity (PCI)of the target cell to the serving network node, e.g. the serving eNodeBin E-UTRAN. The PCI is an identity which identifies the target cell, butit is typically not unique within the network. In current E-UTRANspecifications, for instance, there are only 504 different PCIs defined.This is because the PCI is broadcast at frequent intervals in the cell,so its length is restricted to only a few bytes in order to consume lessradio resources. As a consequence, in a large network the same PCI mayneed to be reused in several cells and is therefore not guaranteed to beunique, or even to uniquely identify the type of the cell. In a denseHome Base Station deployment scenario, the PCIs are more frequentlyreused, due to the large number of cells and smaller cell sizes.

Therefore, in a situation where the serving network node is not able toderive the necessary information from the PCI, the serving network nodemay also request the UE to decode and report the Cell Global Identifier(CGI) of the target cell. For example, based on the reported PCI, thenetwork node may suspect that the target cell belongs to a CSG, a HomeBase Station or to any similar node as part of the heterogeneousnetwork. In order to prevent a HO command to a non-allowed Home BaseStation, e.g. a CSG cell to which the UE does not have access, theserving network node needs to be able to uniquely identify the cell, orat least determine with certainty whether the cell is served by a HBS ornot, and in particular whether it is associated with a CSG. However,since the PCI is not unique, the network node cannot establish thisbased on the PCI alone. The CGI, however, is an identity which is uniquein the network, thereby allowing the network to distinguish betweenmacro BSs and home BSs, or to uniquely identify that the reported cellis associated with a CSG. Hence, to confirm its hypothesis that thetarget cell is served by a HBS, the network may request the UE to decodeand report the target cell's CGI or ECGI.

The procedure and the associated requirements for the UE reporting ofthe target cell's CGI or ECGI are specified in both UTRAN and E-UTRAN.One key aspect of the CGI decoding is that it is performed by the UEduring autonomous gaps, which are created by the UE itself. During theautonomous gaps, the UE interrupts its reception and transmission ofdata in the serving cell. The reason for acquiring the target cell CGIduring autonomous gaps is that the typical UE implementation is notcapable of simultaneously receiving data from the serving cell andacquiring the target cell's system information, which contains the CGI.Furthermore, the CGI acquisition of an inter-frequency or inter-RadioAccess Technology (inter-RAT) target cell requires the UE to switchcarrier frequency, which means it cannot communicate with the servingcell at the same time. Hence, the use of autonomous gaps is necessaryfor acquiring the target cell's CGI. These autonomous gaps are alsointerchangeably referred to as measurement occasions, because the gapsare the occasions during which the UE measures the CGI of the targetcell.

The CGI is sent over a system information block (SIB). In E-UTRAN, theCGI is called E-UTRAN CGI (ECGI), and is transmitted in systeminformation block type 1 (SIB1). However, the acquisition of ECGIrequires the UE to first read the master information block (MIB) of thetarget cell, which is transmitted on the physical broadcast channel(PBCH) with a periodicity of 40 ms. Within the 40 ms period, the PBCH isrepeated in every frame. For example, in E-UTRAN, the length of anE-UTRAN frame is 10 ms, and the PBCH will be repeated in every fourthframe. The MIB enables the UE to acquire information such as systemframe number (SFN), cell transmission bandwidth etc. Hence, afteracquiring the MIB, the UE reads the system information block type 1(SIB1), which contains the ECGI and is transmitted with a periodicity of80 ms on DL-SCH. The home eNodeB can be deployed on a shared carrier oron a dedicated carrier as described earlier. Therefore EGCI requirementsin E-UTRAN are specified for the following two scenarios:

-   -   Intra-frequency ECGI reporting    -   Inter-frequency ECGI reporting

The UE is required to report the intra-frequency ECGI within about 200ms, including processing time of the measurement request, afterreceiving a request from the serving network node, for a targetintra-frequency cell provided that the target cell's SINR experienced bythe UE is at least −6 dB or higher, and to report an inter-frequencyECGI within about 200 ms, including processing time of the measurementrequest, provided that the target cell's SINR is at least −4 dB orhigher. During the acquisition of the target cell's ECGI on the servingcarrier frequency the UE is allowed to create autonomous gaps in thedownlink. Those gaps result in interruptions in the UE downlinkreception from the serving node, and uplink transmission to the servingnode. That is to say, the UE cannot receive signals from or transmitsignals to its serving node during an autonomous gap. The duration ofthe autonomous gap may vary depending upon the UE implementation, buttypically comprises 3 sub-frames.

In UTRAN, the CGI is transmitted in the system information block type 3(SIB3). But in order to read the SIB3 the UE has to first read the MIB.Hence the UE can determine the CGI of a neighbor cell by reading its MIBand system information block type 3 (SIB3), which are sent on thebroadcast channel (BCH). The MIB is transmitted every 20 ms. The SIB3may have different periodicity, which is configured by the network. Ascompared to E-UTRAN, in UTRAN the target cell's CGI acquisition time istypically much longer, e.g. more than 1 second depending upon theperiodicity of the SIB3. Furthermore, due to the autonomous gaps createdby the UE to acquire the target cell's CGI, the interruption of the datatransmission and reception from the serving cell can be 600 ms orlonger.

The concepts of autonomous gaps and CGI/ECGI acquisition are alsorelevant for self organizing networks (SON). The SON function in E-UTRANand UTRAN allows the operator to automatically plan and tune the networkparameters and network nodes. The conventional method is based on manualtuning, which consumes enormous amounts of time and resources, andrequires considerable involvement of work force. Due to networkcomplexity, a large number of system parameters, Inter-Radio AccessTechnologies (IRAT) etc., it is very attractive to have reliable schemesto perform the test of self organization in the network whenevernecessary.

An operator may also add or delete a cell or an entire base station,which may serve multiple cells. Especially new cells are added morefrequently during an early phase of network deployment. In the laterstages, an operator can still upgrade the network by adding morecarriers or more base stations on the same carrier. It can also addcells related to another technology. The network may automaticallydetect the new cells and their relationship to existing cells in aprocess referred to as automatic neighbor cell relation (ANR)establishment, which it is part of the self organizing network (SON)functionality. In order to ensure correct establishment of the neighborcell relation, the serving cell requests the UE to report the CGI of thenew target cell, whose PCI is identified and reported to the saidserving cell. The CGI acquisition requires the UE to read the targetcell's system information and is thus carried out by the UE duringautonomous gaps. As in the case of home inbound mobility, the CGIacquisition for ANR purposes also leads to interruption of data from theserving cell.

As explained above, the UE autonomously creates measurement gaps foracquiring the system information of the target cell to decode its CGI inhome BS inbound mobility scenarios, for ANR purposes, or in any similarscenario. In other words, the length (L) of the measurement gaps andnumber (N) of measurement gaps depend upon the UE itself. No signalingor any related information about the autonomous gaps is exchangedbetween the UE and the serving network node. Since the serving networknode is unaware of the exact occasions and number of autonomous gapscreated by the UE, it does not know when the UE can be convenientlyscheduled without losing data due to the gaps.

One solution to this problem is to not allow the serving network node toschedule the UE during the entire time while the UE is acquiring systeminformation, e.g. decoding the CGI, of a target cell. As mentionedabove, this period is about 200 ms in E-UTRAN and may be over one secondin UTRAN. Thus, this solution leads to a long interruption in thetransmission/reception between the serving cell and the UE while thetarget cell's CGI decoding is performed. This may cause significantdegradation of real time services such as voice.

Another prior art solution is to use an aggressive approach, i.e. tocontinue scheduling the UE during the period when the UE is acquiringsystem information from other cells, without any regard for theautonomous gaps. A drawback of this approach is that if the UE receivesan uplink grant which coincides with an autonomous gap, the UE will notbe able to use the grant. Thus, the associated uplink resources, whichcould potentially have been assigned to another UE, will be wasted. If adownlink transmission to the UE coincides with an autonomous gap, the UEwill not receive the information and retransmission will be required.

The performance degradation resulting from these drawbacks may besignificant, in particular in a dense home base station scenario or inheterogeneous networks, where there are many potential target cells forthe UE to measure on. It is therefore important to minimize the durationof the data interruption from the serving cell while the UE is acquiringsystem information, in particular CGI or ECGI.

There is thus a need in the art for improving the performance ofwireless communication systems, in particular in a scenario when UEs mayneed to acquire system information from neighboring cells.

SUMMARY

It is an object of at least some embodiments of the invention to improveperformance by providing a scheduling mechanism, which is able to takeinto account autonomous gaps created by the UE.

Some embodiments of the present invention provide a solution to theabove problem, whereby a serving network node is able to determine atwhat instances the gaps are autonomously created by the UE for theacquisition of the system information. This determination allows thenetwork to schedule the UE based on its knowledge of when the UE isacquiring the target cell's system information.

According to one embodiment, the present invention comprises a methodimplemented in a radio network node. The method comprises the steps of:

-   -   Requesting the UE to identify the system information of the        target cell,    -   Acquiring at least one UE measurement report of the said target        cell,    -   Determining, based on the said acquired measurement report, the        occasions or time instances during which the UE is not acquiring        the system information of the said target cell, and    -   Scheduling the UE for data reception and/or transmission during        the time instances when UE is not acquiring the system        information.

Particular embodiments of the invention enable the serving network nodeto predict or determine the autonomous gaps created by the UE foracquiring the target cell's system information, which contains the CGI.This prediction makes it possible for the serving network node toschedule the UE in the time periods when there is no autonomous gap,which may contribute to performance improvement and/or betterutilization of resources.

Other particular embodiments provide a method in a radio network nodefor scheduling data transmission and/or reception. According to themethod, the radio network node predicts at least one autonomous gapoccurrence in which user equipments served by the radio network nodewill use autonomously created gaps for acquiring system information froma neighboring base station, and during which the UE is not able toreceive data from, and/or transmit data to, the radio network node. Theradio network node then schedules a user equipment for data transmissionand/or reception in a time period which does not overlap with anypredicted autonomous gap occurrence.

Other particular embodiments provide a method in a radio network nodeserving a user equipment. According to the method, the radio networknode receives information from the user equipment, which indicates atleast one autonomous gap occurrence, during which the user equipmentwill autonomously create gaps for acquiring system information from aneighboring base station. Furthermore, the radio network node predictsat least one autonomous gap occurrence in which user equipments servedby the radio network node will use autonomously created gaps foracquiring system information from the neighboring base station. Theradio network node then schedules a user equipment for data transmissionand/or reception in a time period which does not overlap with anypredicted autonomous gap occurrence.

Another embodiment provides a radio network node comprising one or moreprocessing circuits, which are configured to predict at least oneautonomous gap occurrence in which user equipments served by the radionetwork node will use autonomously created gaps for acquiring systeminformation from a neighboring base station and during which the UE isnot able to receive data from, and/or transmit data to, the radionetwork node. Furthermore, the processing circuits are configured toschedule a user equipment for data transmission and/or reception in atime period which does not overlap with any predicted autonomous gapoccurrence.

Another embodiment provides a radio network node comprising one or moreprocessing circuits, which are configured to receive information from auser equipment being served by the radio network node. The informationindicates at least one autonomous gap occurrence, during which the userequipment will autonomously create gaps for acquiring system informationfrom a neighboring base station. The processing circuits are furtherconfigured to predict at least one autonomous gap occurrence in whichuser equipments served by the radio network node will use autonomouslycreated gaps for acquiring system information from the neighboring basestation. Furthermore, the processing circuits are configured to schedulea user equipment for data transmission and/or reception in a time periodwhich does not overlap with any predicted autonomous gap occurrence.

Another embodiment provides a method in a user equipment, which is beingserved by a radio network node. According to the method, the userequipment performs a measurement on a signal received from a neighboringbase station. Based on this measurement, the user equipment determinesat least one autonomous gap occurrence during which the user equipmentwill autonomously create gaps for acquiring system information from theneighboring base station. The user equipment then transmits informationto the radio network node, indicating the at least one autonomous gapoccurrence.

In another embodiment, a user equipment comprising one or moreprocessing circuits is provided. The processing circuits are configuredto perform a measurement on a signal received from a neighboring basestation, and to determine, based on the measurement, at least oneautonomous gap occurrence during which the user equipment willautonomously create gaps for acquiring system information from aneighboring base station. The processing circuits are further configuredto transmit information to the radio network node serving the userequipment, the information indicating the at least one autonomous gapoccurrence.

An advantage of some embodiments is that the serving cell interruptionwhile the UE acquires the CGI of the target cell is minimized, since theserving cell can still schedule the UE during the occasions when thereare no gaps. This is made possible because the radio network nodepredicts the autonomous gap occurrences that the UE will use to acquiresystem information from the target cells.

A further advantage is that the scheduling grant issued by the servingcell to the UE is not wasted since the serving cell knows when the UEcan transmit and/or receive the data when it is acquiring the systeminformation of the target cell.

Furthermore, the performance degradation of delay sensitive servicessuch as voice over IP can be minimized by reducing the interruption inscheduling the packets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a wireless network.

FIG. 2 is a schematic diagram showing a more detailed view of thewireless network of FIG. 1.

FIG. 3 is a flow chart illustrating a method in a network node accordingto some embodiments.

FIG. 4 is a flow chart illustrating a method according to an embodiment.

FIG. 5 is a flow chart illustrating a method in a base station accordingto some embodiments.

FIG. 6 is a flow chart illustrating a method in a network node accordingto some embodiments.

FIG. 7 is a flow chart illustrating a method in a network node accordingto some embodiments.

FIG. 8 is a flow chart illustrating a method in a network node accordingto some embodiments.

FIG. 9 is a flow chart illustrating a method in a user equipmentaccording to some embodiments.

FIG. 10 is a flow chart illustrating a method in a network nodeaccording to some embodiments.

FIG. 11 is a schematic block diagram illustrating a base station.

FIG. 12 is a schematic block diagram illustrating a user equipment.

LIST OF ABBREVIATIONS

-   CPICH: Common pilot channel-   CSI Channel state information-   E-UTRAN: Evolved UTRAN-   GPS: Global Positioning System-   RSRP: Reference symbol received power-   RSRQ: Reference symbol received quality-   UE: User Equipment-   UTRAN: Universal Terrestrial Radio Access Network-   WCDMA: Wide band code division multiple access-   SON: Self organizing network-   CGI: Cell global identifier-   PCI: Physical cell identifier-   ANR: Automatic neighbor relation

DETAILED DESCRIPTION

It should be noted that although terminology from 3GPP UTRAN, also knownas 3G, and E-UTRAN, also known as Long Term Evolution (LTE), has beenused in this disclosure to exemplify the invention, this should not beseen as limiting the scope of the invention to only the aforementionedsystem. Other wireless systems, including other WCDMA-based systems,WiMax, Ultra Mobile Broadband (UMB) and GSM, may also benefit fromexploiting the ideas covered within this disclosure.

As explained above, the use of autonomous gaps for acquiring systeminformation may result in service interruption and performancedegradation of the ongoing communication between the serving cell andthe UE. However, typically the autonomous gaps created by the UE areshort, sporadic and sometimes occur periodically. This implies that thenetwork could in principle still maintain active communication with theUE, i.e. transmit and/or receive data, while the UE is acquiring the CGIof a neighbor cell, provided that the communication takes place in thetime periods when there is no gap—that is, the serving network node maymore intelligently schedule transmissions to or from the UE, based onknowing or at least predicting, with some accuracy, when the measurementgaps are likely to occur.

This disclosure uses the terms “occurrence”, “occasion”, and “timing”interchangeably when referring to the UE measurement gaps. Herein,“timing” should be broadly construed to include the times and/orpositions of measurement gaps, in an absolute or relative sense (e.g.,with respect to synchronized frames), and/or the number, duration,and/or periodicity of such gaps.

The term “autonomous gap occurrence”, when used in this disclosure,refers to a time instance or a time period, determined or selected bythe UE, when a user equipment is not able to receive data from itsserving network node, because the user equipment is acquiringinformation from another node, e.g. a neighboring base station. In somecases the UE may also not be able to transmit data to its servingnetwork node during the autonomous gap occurrence. As explained above,the time instance or time period may be defined in various differentways, for instance as a starting and ending subframe number, or astarting subframe number and a length, either in milliseconds or interms of number of subframes. The autonomous gap occurrence may also bedefined only by its starting point, e.g. starting subframe number. Inthis case the length of the gap occurrence may be predefined, e.g. thegap length may be assumed to always be 3 subframes.

The following non-limiting example is intended to illustrate thepotential improvement in terms of resource utilization, if the servingnetwork node would be able to predict the autonomous gap occurrences ofthe UE. It is first recalled that in E-UTRAN, the UE is required toacquire and report the CGI of a neighbor cell within about 200 ms,including processing time of the measurement request command. Since theneighbor BS will be transmitting the MIB and SIB1 (which contains CGI)once every 40 ms and 80 ms respectively, there will be either four orfive possible occurrences when the UE may attempt to acquire the CGIwithin this 200 ms period. The contents of MIB and SIB1 are repeatedevery 10 ms and 20 ms during 40 ms and 80 ms periods respectively. Thisenables UE to improve the decoding performance by soft combining the MIBand SIB1 information up to 4 times within their respective periods. TheUE reads MIB and SIB1 in tandem. This is because in order to read SIB1the UE needs to know some fundamental system parameters like celltransmission bandwidth, system frame number (SFN) etc, which aretransmitted in MIB. Assuming that the UE creates an autonomous gap ateach CGI transmission occurrence, and each gap is three subframes inlength, this means that autonomous gaps will occur only in a total of 12or 24 subframes, corresponding to 12 or 24 ms out of the entire 200 msmeasurement period (the length of a subframe in E-UTRAN is 1 ms). Thus,if the network node would be able to accurately predict when the gapswould occur, it could schedule transmissions to or from the UE in theremaining 200−24=176 ms.

In some embodiments of the invention, the serving network node predictsthe autonomous gap occurrences based on the knowledge or assumption thatthe UE will only create a gap when the required system information, e.g.the Master Information Block (MIB), the required SIB (i.e. SIB1 inE-UTRAN and SIB3 in UTRAN) containing CGI etc, is actually beingtransmitted in the neighbor cell, e.g. a target cell for handover. Thus,in the serving network node may predict the autonomous gap occurrencesby determining timing information for the neighboring base station, andthen deducing from the timing information when the required systeminformation, e.g. the ECGI, will be transmitted. That is to say, theserving network node assumes that the timing of the autonomous gaps inthe UE coincides with the timing of the transmission of the requiredsystem information in the neighbor cell. Various methods that theserving network node may use for determining timing information forneighboring base stations are set forth in this disclosure.

In other embodiments, the gaps are predicted based on the absence orpresence of an expected transmission from the UE. For instance, if theserving network node does not receive an expected Channel StateInformation (CSI) report from the UE, or if it does not receive HARQACK/NACK feedback following a downlink transmission, the serving networknode may assume that an autonomous gap occurred, preventing the UE fromreceiving or transmitting information. Conversely, if the servingnetwork node does receive feedback from the UE, it may assume that therewas no gap created during that particular time period. This informationmay be used to predict future autonomous gap occurrences, assuming thatthe gaps recur periodically.

FIG. 1 is a schematic diagram illustrating a wireless network 100 inwhich some embodiments of the invention may operate. The wirelessnetwork 100 comprises three cells 110, 120, 130. A UE may makemeasurements to determine system information for one or more neighboringcells 120, 130, such as to enable reporting of the CGIs of thoseneighboring cells to its reporting cell, or serving cell, 110. Note thatthe uniformity of cells depicted in the drawing does not imply that thereal-world network is so implemented, as different cell types/sizes maybe involved. Regardless, according to particular embodiments of thepresent invention, scheduling of data transmissions to or from the UE isimproved, based on determining the timing of service interruptionscaused in the serving cell by the UE's measurements of neighboring cellsystem information.

FIG. 2 is a schematic diagram which gives a more detailed view of thewireless network 100 shown in FIG. 1. Three UEs 104, 106 and 108 arepresent within the cell 110, and served by the serving base station 102.Neighboring cell 120 is served by base station 122, and neighboring cell130 is served by base station 132. The base stations 102, 122, and 132periodically transmit system information, which can be decoded by UEslocated within the cell coverage area. It is to be understood, withrespect to all embodiments set forth herein, that this particularexample scenario is not to be construed as limiting, and that theexemplified methods and arrangements may be applied in a networkcomprising any number of cells, with any number of UEs being served byeach cell. It is further pointed out that while the example scenario inFIG. 2 shows a single network node serving each cell, it is equallypossible for one network node to serve several cells or sectors.

Referring to FIG. 2 and the flowchart of FIG. 3, a general method forscheduling data transmission and/or reception according to oneembodiment will now be described. The method is performed in a networknode 102, e.g. an E-UTRAN eNodeB or an UTRAN RNC. In a first step 310,the network node 102 predicts at least one autonomous gap occurrence inwhich user equipments 104, 106, 108 served by the network node 102 willuse autonomously created gaps for acquiring system information from aneighboring base station 122. During such an autonomous gap occurrence,the user equipment creating the gap is not able to receive data from,and/or transmit data to, the serving network node 102. In a further step320, the network node 102 schedules a user equipment 104 for datatransmission and/or reception in a time period which does not overlapwith any predicted autonomous gap occurrence. In other words, thenetwork node 102 schedules the UE in the non-gap periods.

Another general method according to some embodiments is illustrated inFIG. 4. According to this method, a base station determines gap timinginformation, and then adapts the downlink and/or uplink scheduling for auser equipment as a function of the gap timing. The expression “gaptiming” as used in FIG. 4 corresponds to “autonomous gap occurrence” inFIG. 3.

In particular embodiments of the invention, one may assume a scenariowhereby in active mode, e.g. RRC_CONNECTED mode in E-UTRAN, the servingnetwork node, e.g. serving eNode B in E-UTRAN, requests that the UE:

-   -   Read the system information of at least one target cell or        neighbor cell, which may operate over the intra-frequency        carrier, inter-frequency carrier or may belong to another Radio        Access Technology (RAT).    -   Acquire CGI of the target cell or neighbor cell by reading the        system information of the target cell during the measurement        gaps, which are created autonomously by the UE without the        intervention of the network.    -   Report the acquired CGI to the serving network node.

According to particular embodiments of the invention, a method in anetwork node is provided. The method comprises the steps of:

-   -   I. Determining, based on static/semi-static and dynamic        information, the occurrence of at least one autonomous gap,        which comprise at least one of the time instances (T0), the        length (L) and the number of autonomous gaps which are to be        created by the UE while acquiring system information, such as        the CGI of a particular target cell.    -   II. Using the determined knowledge in step I) to determine when        the UE can be scheduled without interruption due to the        autonomous gaps.    -   III. Scheduling the UE while taking into account the determined        knowledge.

The subsequent sections describe the use of static, semi-static anddynamic information for the determination of the occurrence ofautonomous gaps according to some embodiments.

The occurrence of gaps may be determined by using static and/orsemi-static information. By static and semi-static information we meanthe information which may change over a longer time scale e.g. in theorder ranging from hours to several days. This type of information cantypically be stored in a database, such as at the time of networkplanning.

The following pieces of static or semi-static information are gatheredby the network and one or more elements of this information can becombined with other information to determine various details related tothe occurrence of the autonomous gaps:

-   -   Scheduling of system information (e.g. SFN, MIB and SIB1) in the        neighboring cells.    -   In case of an asynchronous network, the Frame Start Timing of        the neighboring cells or the time offset between the frame        timing of the serving and the neighbor cells or similar        information. In some cases, the network may already have this        information, if it supports positioning services such as        observed time difference of arrival (OTDOA).    -   In case of a synchronous network, the accuracy of the frame        start timing between the cells and also the cell size, e.g. cell        range or cell radius, of the serving and the neighbor cells,        because the accuracy between any two cells depends upon the        overlapping area between them.    -   UE receiver type or receiver capability information either        explicitly, i.e. by UE indication/capability reporting or        implicitly, which is based on the UE reported measurement        data/results, i.e. based on past UE reported statistics. This        information indicates whether the UE has a baseline receiver or        an advanced receiver, e.g. an interference cancellation        receiver.

As mentioned above, the UE creates gaps only when the required systeminformation (e.g. MIB, the required SIB containing CGI etc) aretransmitted in the target cell. After synchronization to the target celland acquisition of the SFN, the UE will only read the necessary SIBwhich contains the target cell CGI.

Thus, the above information enables the network to determine thepotential time instances (T0) of the occurrences of the autonomous gapsthat can be created by the UE for obtaining the CGI of the target cell,assuming the target cell is at the lowest SNR for which the requirementsare specified (e.g. SNR=−6 dB in case of E-UTRAN intrafrequency).

The static and semi-static information discussed above provideinformation about the scheduling and transmission of the neighbor cells'system information, which for instance contains CGI of the neighborcells. In addition, one or more out of the following set of dynamicinformation indicated below may be used to assist the network node indetermining the number of autonomous gaps and also the length of eachgap the UE may use in decoding the CGI of a particular target cell. Thisdynamic information comprises:

-   -   Signal quality of the target cell    -   Relative signal quality between the serving and the target cell    -   Time required for identifying the physical cell identity of the        target cell    -   Received time difference between the serving and the target cell    -   HARQ ACK/NACK    -   Interruption in periodic CSI reports

A method in a network node for scheduling data transmission and/orreception according to an embodiment of the invention will now bedescribed, with reference to the example scenario of FIG. 2 and theflowchart in FIG. 5.

The method may be executed in a network node 102, comprised within awireless communication network 100 as shown in FIG. 2. The network node102 may for instance be an E-UTRAN eNodeB, or an UTRAN radio networknode such as a NodeB or RNC. The network node 102 serves a cell 110, andwithin this cell three user equipments 104, 106, 108 are located.However, it should be understood that this scenario is not limiting—inparticular, the network node 102 may serve more than one cell, and thecell 110 may comprise any number of user equipments.

In step 510, the network node 102 receives a measurement report from areporting user equipment 104. The measurement report relates to theneighboring cell 120, served by base station 122. For instance, themeasurement report could be a neighbor cell measurement reportcomprising the PCI of neighboring base station 122, as well as otherinformation such as the signal-to-noise ratio, SNR, of neighboring basestation 122 as experienced by UE 104.

In step 520, the network node 102 determines timing information for theneighboring base station 122 based on the measurement report received instep 510. The timing information comprises the frame start timing and/orthe System Frame Number, SFN of neighboring base station 122. In onevariant, the frame start timing and/or SFN are directly included in themeasurement report received from the UE. In another variant, the timinginformation is determined based on the relative time difference betweenthe serving base station 102 and the neighboring base station 122, asmeasured by the UE 104. Especially in an asynchronous network, therelative time difference between the serving and the target cell, asmeasured by the UE 104, may be used by the serving node 102 to determinethe precise transmit timing of the target cell 120. Another possibilityis that the serving base station or the serving radio network nodedetermines the timing without user equipment measurement reports. In onevariant the serving base station or the serving radio network nodedetermines the timing information of the neighbouring base station fromthe message received from the said neighbouring base station or by anyother network node. The received message contains at least the framestart timing and may also contain the SFN of the neighbouring basestation. In yet another variant, the radio network node or the servingbase station directly acquires the timing information of theneighbouring base station by performing correlation over a pre-definedset of synchronization and/or pilot signals transmitted by theneighbouring base station. In order to further acquire the SFN of theneighbour cell the radio network node has to also read at least part ofthe system information (e.g. MIB) of the neighbouring base station. Thismethod requires that the radio network node is equipped with a receiverunit, which is capable of receiving signals transmitted by other radionetwork node such as base stations. Low power network nodes such as homebase stations, relay nodes or pico base stations are generally equippedwith a receiver to receive the signals from other base stations, inparticular macro base stations.

The timing information determined in step 520 enables network node 102to determine when the neighbor cell 120 is transmitting certain systeminformation, such as a certain SIB, or more specifically the Cell GlobalIdentifier, CGI, contained in SIB1 in E-UTRAN. This is because systeminformation is transmitted periodically in certain predefined frames orsubframes—for instance, as explained above, in E-UTRAN the MIB and SIB1which contains the CGI are transmitted every 40 ms or every 4^(th) frameand every 80 ms or every 8^(th) frame respectively. Thus, by knowing theframe start timing and/or the current SFN of the neighboring basestation 122, the network node 102 is able to determine at which futuretime instances or time periods the neighboring base station 122 willtransmit its system information in neighbor cell 120. This informationcorresponds to the potential occasions or instances when the UE 104could create autonomous gaps for acquiring the target cell's 120 CGI.

The network node 102 thus uses the determined timing information in astep 530 for predicting at least one autonomous gap occurrence for userequipments served by network node 102, which are acquiring systeminformation from the neighbor cell 120. In this way, the network node102 determines the starting point in time for one or more gapoccurrences. However, the timing information does not reveal theduration of each gap, or the total number of gaps used by the UE 104 foracquiring the system information. The duration and number of gaps arepreconfigured in this embodiment. For instance, the duration of eachautonomous gap may be preconfigured to be 1, 2, 3, or 4 subframes.

Other preconfigured durations are also possible. As for the total numberof gaps created, in this embodiment the network node 102 assumes thatthe user equipment will use the maximum possible number of autonomousgap occurrences in a measurement period for acquiring the systeminformation such as CGI of the neighbouring base station. For instance,as mentioned above, during a measurement period of 200 ms there will befour or five possible autonomous gap occurrences, depending on when theUE starts to measure. In this embodiment the network node 102 willassume that all these occurrences will be used. It should be noted thatit may be possible for the UE to decode the required system informationfaster, e.g. using only two out of four possible gap occurrences, inwhich case the network node 102 would unnecessarily avoid scheduling theUE during the remaining two or three gaps. However, this is not likelyto cause any significant performance reduction.

In some variants of this embodiment, the network node 102 performs afurther step 550, wherein the network node 102 requests a user equipmentto acquire system information from the neighboring base station 122. Forexample, if the network node 102 received a PCI in step 510, the networknode 102 might determine based on the PCI that the neighboring basestation 122 could be a Home Base Station, but that this cannot bedetermined with certainty based on the PCI alone. To confirm if theneighbor cell 120 really is a Home Base Station, the network node 102may request UE 104 to also acquire the CGI of neighbor cell 120.However, it should be pointed out that after acquiring timinginformation for neighboring base station 122 from UE 104, the networknode 102 could alternatively request another UE, e.g. UE 106 or 108, toacquire system information from neighboring base station 122. That is tosay, network node 102 may use the timing information from UE 104 topredict the autonomous gap occurrences for any of the other UEs 106, 108within cell 110.

In step 560, the network node 102 schedules a user equipment for datatransmission and/or reception in a time period which does not overlapwith any predicted autonomous gap occurrence. That is to say, thenetwork node 102 avoids the gap occurrences during the measurementperiod when the UE is acquiring system information, by scheduling the UEin a time period that does not coincide with any of the gaps. In oneparticular variant, the network node 102 schedules the UE only in timeperiods that do not coincide or overlap with any of the predictedautonomous gap occurrences. It is pointed out that the user equipment tobe scheduled in step 560 could be the reporting UE 104, i.e. the UE thatsent the initial measurement report, but it could also be any other UEserved by the network node 102, provided that the network node 102 isaware that this UE is currently in a measurement period during which itis attempting to acquire system information from the neighboring basestation 122 using autonomous gaps. That is to say, the predicted gapoccurrences for UE 104 may be used to schedule other UEs. In somevariants, the serving network node 102 may gather statistics fromseveral UEs in order to more accurately determine the timing of theneighboring base station 122.

A further embodiment of a method in a network node for scheduling datatransmission and/or reception will now be described, also with referenceto FIG. 5. This embodiment is based on the one described above. However,in this embodiment the duration and/or number of gap occurrences are notpreconfigured. Instead, additional information is used to more preciselydetermine the gap occurrences, i.e., the number of gap instances and/orlength, i.e. duration, of each instance.

Thus, in the present embodiment steps 510, 520, 530, and the optionalstep 550, are performed in the same way as described above.

However, this embodiment comprises an additional step 540, wherein thenetwork node 102 predicts the duration and/or number of the autonomousgap occurrences that will be used by the UE 104 for acquiring systeminformation from the neighbouring base station 122.

In some variants of this embodiment, the serving network node 102predicts the duration and/or number of gap occurrences based on the SNRof the neighboring base station 122. At higher SNR (i.e. higher RSRQ) ofthe target cell 120, the UE requires fewer gaps to decode the CGI. Onthe other hand, at lower SNR level the UE may require more gaps, and inthe worst case may require all possible gaps within the maximum allowedtime. The network may maintain a pre-defined mapping between the SNR andthe number of measurement gaps required for acquiring the CGI of thetarget cell for different UE receiver types. The duration of each gapdepends on the SNR of neighbor cell 120 in a corresponding way. That isto say, at a higher SNR, the UE 104 may be able to decode the systeminformation using fewer subframes than at a lower SNR. At lower SNRlevels, a larger gap, i.e. a longer gap, might be needed due to highernoise level and imprecise received timing from a weak target cell.

The following paragraphs will describe several ways in which the servingnetwork node 102 may determine the SNR of the neighboring base station122.

In one variant, the serving network node 102 assumes the lowest allowedSNR of the target cell or neighbor cell 120 (e.g. SNR=−6 dB) todetermine the number of measurement occasions, i.e. autonomous gapoccurrences, for a particular receiver type based on the pre-definedmapping.

In another variant, the serving network node 102 determines the SNRbased on a signal quality measurement. The signal quality reveals theSNR or signal strength of the target cell. Examples of such measurementsare RSRQ and RSRP of the target cell in E-UTRAN and CPICH Ec/No andCPICH RSCP in UTRAN.

These signal quality metrics are generally reported with the PCI of theidentified target cell in prior art. Alternatively, the serving networknode can preconfigure the UE 104 to report one or more of thesemeasurements whenever a new neighbor cell is identified. Thus, theserving network node 102 may receive one or more of these metrics aspart of the measurement report received in step 510. In the presentvariant, one or more of these signal quality metrics is used indetermining or predicting the occurrence of the service gaps, i.e. theautonomous gap occurrences, caused by the UE in decoding the CGI of thetarget cell. For instance, as mentioned above, the network can maintaina pre-defined mapping between the number of gaps required to decode CGIand the corresponding signal quality, e.g. SNR, RSRQ and RSRP. As statedearlier, the CGI acquisition requires the UE to decode MIB and SIB.Hence, separate pre-defined mapping tables for determining the gaps fordecoding the MIB and SIB may be used in some embodiments. Such a mappingtable may also be used to predict the size of each gap e.g. whether eachgap should be 2 ms or 4 ms long. Hence using the reported measurementand mapping tables, the network node can determine when it is feasibleto schedule the UE, i.e., when UE completes the acquisition of CGI. Thereported measurement and the mapping table also reveal to the network,i.e. the serving network node 102, when the UE will complete thedecoding of CGI. For example the UE may require lower overall delaycompared to the minimum requirements in case of high SNR. Hence thenetwork can predict when it can resume scheduling a UE which isperforming CGI decoding.

In another variant, the serving network node 102 uses the relativequality between the serving cell 110 and the target cell 120 todetermine the SNR. The UE 104 may be configured to report an event whichis based on the comparison between the serving and target cell signalstrength or quality, e.g. when the target cell signal quality is X dBabove that of the serving cell 110. The UE 104 also reports the servingcell quality (e.g. RSRQ or RSRP). Using this set of information, theserving network node 102 may determine the target cell's 120 signalquality. The derived target cell quality can then be used to determinethe number of measurement gaps and/or the length of each gap in time,required for acquiring system information, such as the CGI of the targetcell 120. It is pointed out that the UE 104 may report the signalstrength or quality of the neighboring base station 122 relative to thatof the serving base station 102, or vice versa.

In yet another variant, the network node 102 uses the time required foridentifying the PCI of the target cell to determine the signal qualitylevel. For example, at high SNR levels (e.g. 0 dB) the UE 104 is able toidentify the PCI of an unknown neighbor cell in about 50-100 ms innon-DRX, or for DRX in up to 40 ms. However, at a SNR level of −6 dB,the time required to identify the cell is about 800 ms in non DRX state.Thus, by knowing the delay in acquiring the PCI, the network node 102may determine the target cell's 120 SNR, which is turn is used to findthe number and/or size, i.e. duration, of each gap for acquiring systeminformation, such as the CGI of that target cell 120, for example byusing the pre-defined mapping table between SNR and number of gapsand/or length of gaps as described above.

In another variant, the serving network node 102 predicts the durationand/or number of autonomous gap occurrences based on the receivercapability of the user equipment. For instance, if the UE is equippedwith a more advanced received, the network node 102 may assume that itis able to acquire system information using shorter and/or fewer gapoccurrences. Advanced receivers, which may be employed in the userequipment, are generally capably of eliminating or minimizing theintra-cell interference or both intra-cell and inter-cell interference.Some of the advanced receivers that may be employed in the userequipment are also capable of eliminating or minimizing the inter-streaminterference, which occurs due to the multi-stream transmission in caseof Multiple Input Multiple Output (MIMO). These interferencecancellation or minimization capabilities of the advanced receivers inthe user equipment in turn enhance the measured SINR and enable theacquisition of the information in fewer decoding attempts, i.e. in ashorter time.

In another variant, the serving network node 102 uses knowledge ofwhether the serving radio base station and the neighboring base stationoperate on the same or different carrier frequencies to predict theduration of the autonomous gap occurrences. As explained above, the UEis required to switch carrier frequency in order to acquire systeminformation, such as CGI, from an inter-frequency or inter-RAT targetcell, and therefore a longer autonomous gap will typically be needed insuch situations.

In at least one of the variants described above, the network schedulesthe UE in a step 560 to avoid sending and/or receiving during the timesthat the UE is reading the system information. In this regard, thenetwork uses its knowledge of the timing, duration and number of theservice gaps, i.e. autonomous gap occurrences, and schedules aroundthose gaps, e.g., the serving node defers scheduling the UE until afterthe UE reads the system information. It is pointed out that the userequipment to be scheduled in step 460 could be the reporting UE 104,i.e. the UE that sent the initial measurement report, but it could alsobe any other UE served by the network node 102, provided that thenetwork node 102 is aware that the UE is currently in a measurementperiod during which it is attempting to acquire system information fromthe neighboring base station 122 using autonomous gaps. That is to say,information acquired from one UE may be used to predict autonomous gapoccurrences for other UEs. In some variants, the serving network node102 may gather statistics from several UEs in order to more accuratelydetermine the timing, duration and/or number of autonomous gapoccurrences.

In some further variants, the serving network node 102 uses a predictedduration and/or number of gap occurrences, which has been determinedbased on measurements from a first UE, only for those other UEs whichhave similar capabilities as the first UE. and/or are located within acertain distance from the first UE. This is because UEs which have thesame or similar receiver capabilities are more likely to require asimilar duration and/or number of gaps for decoding, as explained above.Furthermore, UEs which are located closer to each other are more likelyto experience a similar SNR with respect to neighboring base station122, and consequently to require a similar duration and/or number ofautonomous gaps, than UEs which are located further apart in the cell110. Therefore, in this variant the network node 102 may be able topredict the duration and/or number of gap occurrences with even higheraccuracy.

A further embodiment of a method in a network node for scheduling datatransmission and/or reception will now be described with reference toFIG. 6. This embodiment is based on the embodiments described above withreference to FIG. 5. Thus, this method may also be executed in a networknode 102, comprised within a wireless communication network 100 as shownin FIG. 2.

In a first step 610, the network node 102 receives a message fromanother network node. The message may for instance be received from theneighboring base station 122, from a positioning node, or from an O&Mnode residing within the wireless communication network 100. The messagecomprises information related to the timing of the neighboring basestation 122, e.g. frame start timing, SFN, relative time differencebetween the serving cell 110 and neighbor cell 120, or any other datathat may be used to derive the neighbor cell timing. In one variant, themessage is a positioning-related message.

The serving network node 102 then proceeds to step 620, where itdetermines timing information for the neighbor cell 120 based on themessage received in step 610. The determined timing informationcomprises the frame start timing and/or the System Frame Number, SFN ofneighbor cell 120.

Once the serving network node 102 has determined the timing ofneighboring base station 122, it proceeds to predicting one or more gapoccurrences in step 530, and scheduling the UE in a time period notoverlapping with any predicted gap occurrence in step 560. Optionally,the serving network node 102 may also perform steps 540 and/or 550.Steps 540-560 may be performed in the same way as described inconnection with FIG. 5 above.

A method in a network node for scheduling data transmission and/orreception according to an embodiment of the invention will now bedescribed, with reference to the scenario of FIG. 2 and the flowchart inFIG. 7. This embodiment predicts autonomous gap occurrences based onHARQ ACK/NACK feedback from a UE.

The method may be executed in network node 102, comprised within awireless communication network 100 as shown in FIG. 2. The network node102 may for instance be an E-UTRAN eNodeB, or an UTRAN NodeB. Thenetwork node 102 serves a cell 110, and within this cell three userequipments 104, 106, 108 are located.

Referring now to FIG. 7, in step 710 the network node 102 transmits datato user equipment 104, which is located within cell 110 and being servedby network node 102.

The transmission of data occurs in a time period when the network node102 knows or suspects that UE 104 is attempting to acquire systeminformation from the neighboring base station 122. For instance, in anE-UTRAN system the transmission of data in step 710 may take placeduring the 200 ms period when UE 104 is acquiring the CGI of neighboringbase station 122 following a request from the serving network node 102.

In a variant of this embodiment, the network node 102 transmits dummydata to the UE in step 710 to check whether the said UE is currentlyusing autonomous gaps or not for measuring the target cell's CGI, i.e.the transmission does not contain any real data destined for the UE. Forinstance, in E-UTRAN the network node 102 may schedule dummy data onPDSCH to UE 104. This may be advantageous in a situation where thenetwork node 102 does not currently have any data pending fortransmission to the UE 104.

In step 720, network node 102 determines whether an autonomous gapoccurrence was used by UE 104 during the time period of the transmissionin step 710. This determination is based on whether the radio networknode 102 receives HARQ NACK/ACK feedback for the transmitted data.

As explained earlier, the HARQ ACK/NACK sent by the UE 104 to theserving network node 102 in response to the transmission in step 710 mayreveal whether the autonomous gaps are currently employed by the UE 104or not. In particular, if the UE does not respond to downlinktransmission from the serving network node 102 in terms of ACK/NACKfeedback, the serving network node 102 may assume that an autonomous gapoccurrence is being used by the UE 104 for decoding system information,such as the CGI of neighbor cell 120. Similarly, if the UE 104 sends anACK/NACK response to a downlink transmission, then the network node 102may assume that the UE 104 is not currently creating an autonomous gapoccurrence, and hence the network, if needed, may continue schedulingthe UE 104.

Based on the information about past or current gap occurrences which wasdetermined in step 720, the network node 102 predicts in step 730 atleast one autonomous gap occurrence in which its served UEs willautonomously create gaps for acquiring system information fromneighboring base station 122. That is to say, the network node 102predicts that the future gap occurrences will correspond to the past orcurrent gap occurrences. For example, in an E-UTRAN scenario where theUE 104 is acquiring the ECGI from neighboring base station 122, thenetwork node 102 may predict that the next gap occurrence will occur 40ms from the last detected gap occurrence, since in E-UTRAN the ECGI istransmitted with a periodicity of 40 ms.

In some variants, the network node 102 may also predict the durationand/or length of the autonomous gaps based on the HARQ ACK/NACK feedbackin a step 740. For example, the network node 102 may determine theduration and/or number of times when the UE 104 did not provide any HARQfeedback, and then predict that the same or a similar duration and/ornumber of gaps will also apply to future autonomous gap occurrences. Asan example, the network node 102 may repeat steps 710 and 720 two ormore times to obtain more detailed information as to the duration of thegap and/or the number of occasions. If the network node 102 has accessto UE capability information, this information may also be used tobetter predict the duration and/or number of gaps required by the UE104, as described in connection with previous embodiments.

In other variants, the duration and/or number of the gaps may bepreconfigured, e.g. the duration may be assumed to be 2-4 subframes andthe number of gaps may be assumed to be all possible gap occurrences, asdescribed above.

In some variants of this embodiment, the network node 102 performs step550, wherein the network node 102 requests a user equipment to acquiresystem information from the neighboring base station. This step may beperformed in a way similar to that described in connection with previousembodiments.

In step 760, network node 102 schedules a user equipment for datatransmission and/or reception in a time period which does not overlapwith any of the autonomous gap occurrence which were predicted in step730. According to one variant, the UE is scheduled only in time periodswhich do not coincide with any predicted gap occurrence.

In a particular variant of this embodiment, the network node 102collects statistics of the HARQ ACK/NACK feedback, i.e. interruption inACK/NACK when UE 104 decodes system information such as CGI. Thisessentially corresponds to performing steps 710 and 720 multiple times,and possibly for different user equipments. The network node 102 usesthe statistics to determine the pattern of the autonomous gaps createdby the UE 104 while the UE decodes system information, e.g. CGI, of atarget cell 120 under a certain target cell SNR. A more precise patternof gaps can be determined by the serving node 102 by combining thetarget cell SNR (e.g. RSRQ as explained above) and the HARQ ACK/NACKstatistics. Such a pattern based on the statistics and target cell SNRcan be used by the network node 102 in the future when performingscheduling while the UE 104 acquires system information, e.g. the CGI,of the target cell 120.

Similarly to previous embodiments, it is pointed out that the userequipment to be scheduled in step 760 could be the UE 104, i.e. the UEthat the network node transmitted data to in step 610, but it could alsobe any other UE served by the network node 102, provided that thenetwork node 102 is aware that the UE is currently in a measurementperiod during which it is attempting to acquire system information fromthe neighboring base station 122 using autonomous gaps. That is to say,HARQ ACK/NACK feedback acquired from one or more UEs may be used topredict autonomous gap occurrences for other UEs which are acquiringsystem information from neighbor cell 120, in particular for UEs havingsimilar receiver capabilities.

The present embodiment may be combined in various ways with any of thepreviously described embodiments. As mentioned above, the HARQ ACK/NACKfeedback information or statistics described in this embodiment may becombined with SNR and/or UE capability information. Furthermore, thenetwork node 102 may determine the timing of neighbor cell 120 in any ofthe ways described above, and combine this information with HARQfeedback data or statistics to make the prediction of autonomous gapoccurrences even more accurate.

A method in a network node for scheduling data transmission and/orreception according to an embodiment of the invention will now bedescribed, with reference to the scenario of FIG. 2 and the flowchart inFIG. 8. This embodiment predicts autonomous gap occurrences based on CSIfeedback reports from a UE.

In prior art, the serving network node 102 may configure a UE 104 toperiodically report one or more types of channel state information(CSI), which reveals downlink channel or radio conditions. Thesemeasurements are done over the downlink signals from the serving cell110 and reported to the serving radio network node 102, which in turnuses this for various purposes such as for scheduling, resourceallocation, link adaptation, antenna selection in case of MIMO, rankadaptation in case of MIMO etc. Examples of CSI are channel qualityindicator (CQI), pre-coding matrix index (PMI), rank indicator (RI) etc.

The method may be executed in network node 102, comprised within awireless communication network 100 as shown in FIG. 2. The network node102 may for instance be an E-UTRAN eNodeB, or an UTRAN NodeB. Thenetwork node 102 serves a cell 110, and within this cell three userequipments 104, 106, 108 are located.

Referring now to FIG. 8, in step 810 the network node 102 monitorsreceived reports of Channel State Information, CSI, from a userequipment 104, which is served by the network node 102 and which iscurrently attempting to acquire system information from the neighboringbase station 122.

In some variants of this embodiment, the serving network node 102 startsmonitoring the CSI reporting pattern from the UE 104 after requestingthe UE 104 to acquire the target cell's 120 system information, e.g.CGI.

In step 820, the network node 102 determines whether an autonomous gapoccurrence was created by the user equipment 104, based on the presenceor absence of a CSI report in the time period during which the networknode 102 is monitoring received CSI reports. That is to say, if thenetwork node 102 receives a CSI report it may assume that the UE 104 wasnot using an autonomous gap occurrence in the time instance when the CSIreport was generated, and conversely if the network node 102 does notreceive a CSI report when expected, the network node 102 may infer thatthe UE 104 was prevented from sending a CSI report because of anautonomous gap occurrence.

Based on the information about past or current gap occurrences which wasdetermined in step 820, the network node 102 predicts in step 830 atleast one autonomous gap occurrence in which its served UEs will useautonomously created gap occurrences for acquiring system informationfrom neighboring base station 122. That is to say, the network node 102predicts that the future gap occurrences will correspond to the past orcurrent gap occurrences.

In some variants, the duration and/or number of the autonomous gaps maybe preconfigured, i.e. the duration may be assumed to be 2-4 subframesand the number of gaps may be assumed to be all possible gapoccurrences, as described above. In other variants, the duration and/ornumber of gaps is predicted, for instance based on the presence orabsence of several CSI reports. The duration and/or number of gaps mayalso be determined in any of the ways described above, e.g. based onSNR, UE receiver capability, etc.

In step 860, network node 102 schedules a user equipment for datatransmission and/or reception in a time period which does not overlapwith any of the autonomous gap occurrences which were predicted in step830. According to one variant, the UE is scheduled only in time periodswhich do not coincide with any predicted gap occurrence.

In some variants of this embodiment, the network node 102 collectsstatistics of the CSI reporting interruptions, and uses these statisticsto determine the pattern of the autonomous gaps created by the UE 104while the said UE decodes the system information, e.g. CGI, of a targetcell 120 under certain target cell's SNR. A more precise pattern of gapscan be determined by the serving node 102 by combining the target cellSNR (e.g. RSRQ as explained above) and the CSI interruption statistics.Such a pattern based on the CSI interruption statistics and target cellSNR may be used by the network node 102 in the future when performingscheduling while the UE 104 acquires the CGI of the target cell.

The present embodiment may be combined in various ways with one or moreof the previously described embodiments to obtain more detailed oraccurate information about the timing, duration and/or number of gaps.For example, the CSI interruption statistics may be combined with one ormore of neighbor cell timing, UE capability information, and/or neighborcell SNR measurements, which may all be determined as described above.

A method in a user equipment according to an embodiment of the inventionwill now be described, with reference to the scenario of FIG. 2 and theflowchart in FIG. 9. In this embodiment, an explicit message is sentfrom the UE, comprising information about a past or current autonomouscap occurrence. The serving network node may use this information topredict future autonomous gap occurrences.

The method is executed in a user equipment 104, comprised within awireless communication network 100 as shown in FIG. 2, and being servedby a radio network node 102. The serving radio network node 102 may bean E-UTRAN eNodeB, an UTRAN NodeB or an UTRAN RNC.

In a step 910, the user equipment 104 performs a measurement on a signalreceived from a neighboring base station 122. In one variant the step ofperforming a measurement comprises reading system information, such asthe Cell Global Identifier, CGI, of the neighboring base station 122.

In step 920, the user equipment 104 determines, based on themeasurement, at least one autonomous gap occurrence during which theuser equipment will autonomously create gaps for acquiring systeminformation, e.g. CGI, from the neighboring base station 122.

In some variants of this embodiment, the serving radio network node 102explicitly requests the UE 104 to supply information about theautonomous gap occurrence, and the UE 104 receives this request in astep 930. However, it is also possible for the UE to proceed directlyfrom step 920 to step 940 without receiving any request from the networknode. Furthermore, it should be noted that the request from the networknode may also be received before step 910 is performed, or alternativelybetween steps 910 and 920.

In step 940, the user equipment 104 transmits information to the networknode 102 indicating the at least one autonomous gap occurrence. Forexample, the information indicating the autonomous gap occurrence maycomprise at least one of the starting time or subframe, the number ofgaps, the duration of each gap and the total duration to acquire thesystem information. In a particular variant of this embodiment, theinformation about the autonomous gap occurrence signalled by the UE 104in step 940 corresponds to the actual autonomous gap occurrence whichwas used by the UE 104 for acquiring the system information of theneighbouring base station 122. The information about the autonomous gapoccurrence signalled by the user equipment also includes an identifierof the neighbouring base station, e.g. CGI and/or PCI.

In a variant of this embodiment, the information about the autonomousgap occurrence is separately reported by the user equipment to thenetwork node 102 for gaps created in the uplink and downlink. Anadvantage of this approach is that the user equipment may report theinformation about the autonomous gap occurrence anytime, without waitingfor the normal measurement reporting instances.

According to some variants, the information about the autonomous gapoccurrence is signalled by the UE 104 when reporting measurements suchas downlink signal quality, downlink signal strength, physical cellidentity or global cell identity etc. This approach has an advantage ofreduced signalling overhead, since the information about the gapoccurrence is piggybacked with the normal measurement reports.

The information transmitted to the network node 102 in step 940 enablesthe network node 102 to make predictions about future gap occurrencesfor this UE or other served UEs. The reported information about theautonomous gap occurrence may also be used by the network to performsite planning and/or setting radio parameters, such as the transmittedpower in the base station. For examples the network can increase thetransmit power level of a base station which generally requires userequipments to create more gaps than a certain threshold for acquiringits SI. The increase in the base station's transmitted power level mayimprove the SINR experienced by the user equipment, thereby reducing thelength of the measurement period required for acquiring the SI of thebase station.

A method in a radio network node for scheduling data transmission and/orreception according to an embodiment of the invention will now bedescribed, with reference to the scenario of FIG. 2 and the flowchart inFIG. 10. In this embodiment, the radio network node receives an explicitmessage from the UE, comprising information about a past or currentautonomous cap occurrence, and uses this information to predict futureautonomous gap occurrences.

The method is executed in a radio network node 102, comprised within awireless communication network 100 as shown in FIG. 2. The radio networknode 102 serves a user equipment 104. The serving radio network node 102may be an E-UTRAN eNodeB, an UTRAN NodeB or an UTRAN RNC.

In step 1020, the network node 102 receives information from the userequipment (104) indicating at least one autonomous gap occurrence,during which the user equipment 104 will autonomously create gaps foracquiring system information from a neighboring base station 122. Forexample, the information indicating the at least one autonomous gapoccurrence may comprise one or more of: the starting point of the gapoccurrence, e.g. in the form of a subframe number, the end point orduration of a gap occurrence, and the number of gap occurrences usedduring a system information measurement period. In some variants, theinformation indicating the autonomous gap occurrence is received inconjunction with a measurement report from the user equipment 104, forinstance a neighbor cell report.

In step 1030, the network node 102 predicts at least one autonomous gapoccurrence in which user equipments served by the radio network node 102will use autonomously created gaps for acquiring system information fromthe neighboring base station 122. The prediction is based on theinformation received in step 1020, i.e. the network node 102 assumesthat future gap occurrences will follow the same pattern as the gapoccurrence indicated in step 1020. In some variants, the prediction maybe further improved by combining this method with any of the previouslydescribed embodiments. For instance, timing information related toneighboring base station 122 may be obtained and used to predict thestarting point of the gaps. Furthermore, UE receiver capabilityinformation, SNR, or other metrics may be used to more accuratelypredict the duration and/or number of autonomous gaps. It is alsopossible to combine the present embodiment with information gatheredfrom HARQ/NACK feedback report, or CSI reporting patterns, as alreadyexplained above.

In step 1040, the network node 102 schedules a user equipment for datatransmission and/or reception in a time period which does not overlapwith any predicted autonomous gap occurrence. It should be noted, as forprevious embodiments, that the UE to be scheduled may be the userequipment 104, or another UE which is acquiring system information fromthe neighboring base station 122.

In some variants of this embodiment, a further step 1010 is performedbefore step 1020. In step 1010, the network node 102 requests the userequipment 104 to signal the information indicating the at least gapoccurrence.

As stated earlier, all of the above embodiments may also be used todetermine the autonomous gaps which are created by the UE for readingthe target cell system information when UE is in DRX state. In E-UTRANthe DRX cycles may range from 10 ms to 2.56 seconds.

The network may configure the UE with a DRX cycle such that the DRX ONperiod does not coincide or overlap with the scheduling of systeminformation (SI), especially the MIB and required SIB (e.g. SIB1 inE-UTRAN when reading the CGI), which are to be read by the UE, in thetarget cell. This will ensure that the UE does not create autonomousgaps during the DRX ON periods of the DRX cycle, since these gaps aremeant to read the SI. The UE opens its receiver for the reception of thedata from the serving cell during the DRX ON period, which may comprisebetween a few OFDM symbols up to few sub-frames in E-UTRAN.

For instance, the periods when the SI is being transmitted in the targetcells, i.e. the periods when autonomous gap occurrences may be used, maybe determined using any of the methods described above. Accordingly, theDRX cycle is configured to avoid conflict between the DRX ON period andthe autonomous gaps. This can be easily achieved in a synchronousnetwork since all the cells have the same transmit timing. However in anasynchronous network, the serving network node can set the DRX cycle toavoid, to the extent possible, the conflict with the scheduling of theSI and thus with the potential autonomous gaps when the UE reads the SI.The network may also adjust the DRX cycle to avoid such a conflict withthe scheduling of the SI at the target cell when the network noderequests the UE to read the SI of the target cell. Another possibilityis to use the same measurement period for decoding the CGI of the targetcell in non DRX and for all DRX cycles, regardless of their length. Thiswill ensure that the UE performs the CGI decoding in a shorter time, andthus the risk that the DRX ON period coincides with the autonomous gapsis minimized.

Thus, any of the previously described methods executed in a network nodemay comprise a further step of configuring the DRX cycle of the userequipment to be scheduled, such that the DRX ON periods do not overlapwith any predicted autonomous gap occurrence. In a further variant, thesame duration is used for acquiring the system information of theneighbouring base station regardless whether DRX is used or not, andregardless of the length of the DRX cycle when DRX is used.

FIG. 11 is a block diagram of a base station 1100 according toparticular embodiments of the invention. The example base stationprovides a non-limiting illustration of communication and processingcircuits used in carrying out the network-side of the present inventionin one or more embodiments. However, it should be noted that othernetwork nodes may be involved.

Further, those of ordinary skill in the art will appreciate that theexample base station may well include elements not shown in thesimplified illustration—e.g., additional communication interfaces andprocessing/control circuitry.

Those of ordinary skill in the art will also appreciate that the basestation may be implemented using fixed and/or programmable circuitry. Inone embodiment, the apparatus includes one or more microprocessors,digital signal processors, or other digital processing circuits, alongwith associated program and data memory. As such, the term “circuitry”should be understood as encompassing discrete electronic circuits and/orintegrated electronic circuits (whether fixed or programmable).

For example, in the illustration, the apparatus 1100 comprises one ormore processing circuits 1120 that are configured to implement at leastsome of the network-side processing disclosed herein for the presentinvention. Those one or more processing circuits—e.g., the signallingcontrol circuitry, the gap estimation processor, and the schedulingprocessor—may be at least partly implemented using programmable digitalprocessing circuits. For example, these functions may be implemented inone or more microprocessors, signal processors, or other computercircuits.

In a particular example, the base station's processing circuits 1120 areconfigured to implement the gap timing estimation and correspondingscheduling controls based on the execution of stored computer programinstructions. In that regard, it will be appreciated that these basestation processing circuits 1120 are specially adapted or otherwiseconfigured to carry out the processing disclosed herein, irrespective ofwhether they comprise fixed or programmable circuitry, or any mixthereof. It will also be appreciated that the base station 1100 includesor has access to memory or another computer-readable medium, for storingconfiguration and operating data, which can include information at leastsome of the static/semi-static and dynamic information describedherein—some static information may be provisioned or otherwisepre-stored in the base station for its use during operation.

In one embodiment, the illustrated base station 1100, or variations ofit, is configured to implement a method of improved data schedulingcomprising:

determining timing information regarding gaps in service with the userequipment, as caused by the user equipment measuring system informationfor a neighboring target cell; and

adapting scheduling of data transmissions to or from the user equipmentas a function of the determined timing information.

In one embodiment, said determining comprises estimating, calculating,or otherwise predicting the timing, number, period, or othercharacteristics of such gaps, based on static or semi-staticinformation. Such information comprises knowledge of transmissionframe/sub-frame start timing in the neighboring cells, the scheduling ofsuch information in the neighboring cells, the user equipment'scapabilities, e.g., as regards its measurement of such information, etc.Further, the determination accuracy is enhanced in one or moreembodiments, by basing the determination on dynamic information, such assignal qualities, timing differences, etc.

In another embodiment, the one or more processing circuits 1120 areconfigured to predict at least one autonomous gap occurrence in whichuser equipments served by the radio network node 1100 will useautonomously created gaps for acquiring system information from aneighboring base station and during which the UE is not able to receivedata from, and/or transmit data to, the radio network node, and furtherconfigured to schedule a user equipment for data transmission and/orreception in a time period which does not overlap with any predictedautonomous gap occurrence. In a variant of this embodiment, the one ormore processing circuits 1120 are further configured to request the userequipment to read system information from the neighboring base station.

In a further variant, the one or more processing circuits 1120 arefurther configured to determine when the neighboring base stationtransmits system information. For example, the one or more processingcircuits 1120 may be configured to determine timing information for theneighbouring base station, the timing information comprising at leastone of frame start timing and the System Frame Number, SFN. In avariant, the one or more processing circuits 1120 are further configuredto determine timing information based on a measurement report receivedfrom a reporting user equipment, which is served by the radio networknode, and wherein the measurement report relates to the neighboring basestation. In a further variant, the one or more processing circuits 1120are configured to determine the frame start timing and the SFN aredetermined based on a message received from another network node. In analternative variant, the one or more processing circuits 1120 areconfigured to determine the timing information by performing correlationover a pre-defined set of synchronization and/or pilot signalstransmitted by the neighbouring base station. In some variants, the oneor more processing circuits 1120 are further configured to predict theduration and/or number of autonomous gap occurrences. For instance, theone or more processing circuits 1120 may be configured to predict theduration and/or number of autonomous gap occurrences based on thedownlink signal strength or quality of the base station reported by thereporting user equipment. Furthermore, the one or more processingcircuits 1120 may be configured to predict the duration and/or number ofautonomous gap occurrences based on the time required by the reportinguser equipment to identify the physical layer identity of theneighbouring base station. The one or more processing circuits 1120 mayalso be configured to predict the duration and/or number of autonomousgap occurrences based on the receiver capability of the reporting userequipment. Furthermore, the one or more processing circuits 1120 may beconfigured to predict the duration and/or number of autonomous gapoccurrences based on whether the serving radio radio network node andthe neighboring base station operate on the same or different carrierfrequencies. Alternatively, the duration and/or number of autonomous gapoccurrences may be preconfigured. For instance, the preconfiguredduration of the autonomous gap occurrences may be between 2 and 4subframes. The number of autonomous gap occurrences may be configured tobe the maximum number of autonomous gap occurrences possible within ameasurement period.

In some variants, the one or more processing circuits 1120 areconfigured to transmit data during a certain time period to a userequipment, which is served by the radio network node and which has beenrequested to read system information from the neighboring base station.Furthermore, the one or more processing circuits 1120 are configured todetermine, based on whether the radio network node receives HARQNACK/ACK feedback for the transmitted data, whether an autonomous gapoccurrence was used in the certain time period. In some variants, theone or more processing circuits 1120 are configured to transmit dummydata during the certain time period.

In some variants, the one or more processing circuits 1120 areconfigured to monitor the received reports of Channel State Information,CSI, from a user equipment, which is served by the radio network nodeand which has been requested to read system information from theneighboring base station. Furthermore, the one or more processingcircuits 1120 are configured to determine whether an autonomous gapoccurrence was created by the user equipment, based on the presence orabsence of a CSI report in a certain time period.

In some variants, the one or more processing circuits 1120 are furtherconfigured to configure the DRX cycle of the user equipment to bescheduled such that the DRX ON periods do not overlap with any predictedautonomous gap occurrence. In some variants, the one or more processingcircuits 1120 are configured to use the same measurement period foracquiring the system information of the neighbouring base stationregardless whether DRX is used or not and regardless of the length ofthe DRX cycle when DRX is used.

In yet another embodiment, the one or more processing circuits 1120 areconfigured to receive information from a user equipment being served bythe radio network node 1100, the information indicating at least oneautonomous gap occurrence, during which the user equipment willautonomously create gaps for acquiring system information from aneighboring base station, and further configured to predict at least oneautonomous gap occurrence in which user equipments served by the radionetwork node 1100 will use autonomously created gaps for acquiringsystem information from the neighboring base station. Furthermore, theprocessing circuits 1120 are configured to schedule a user equipment fordata transmission and/or reception in a time period which does notoverlap with any predicted autonomous gap occurrence. In some variants,the one or more processing circuits 1120 are further configured torequest the user equipment to signal the information indicating the atleast gap occurrence.

FIG. 12 is a schematic block diagram illustrating an example item ofuser equipment, such as cellular telephone, smart phone, PDA, networkmodem card, or essentially any other wireless communication apparatus.One sees that the example UE 1200 includes a transceiver 1230 forreceiving DL signals, i.e. control and data, from a supporting network,and for sending UL signals, i.e. control and data, to that network. Onealso sees various processing and control circuits 1220, for processingand responding to received control and data, and for generating controland data for transmission. In particular, the UE may include measurementcircuitry for measuring various received signal parameters, and forobtaining system information from neighboring target cells.

Those ordinarily skilled in the art will appreciate that the UE 1200 ofFIG. 11 may be implemented using fixed or programmable circuits, orboth, and that in one or more embodiments, the UE 1200 includes one ormore microprocessors, digital signal processors, or other such digitalprocessing circuits, and that the UE 1200 may store computer programinstructions, which, when executed, cause the UE 1200 to perform asdescribed herein.

In one embodiment, the illustrated user equipment 1200, or variations ofit, comprises one or more processing circuits 1220, configured toperform a measurement on a signal received from a neighboring basestation, and to determine, based on the measurement, at least oneautonomous gap occurrence during which the user equipment willautonomously create gaps for acquiring system information from aneighboring base station, and to transmit information to the radionetwork node serving the user equipment 1200, the information indicatingthe at least one autonomous gap occurrence.

In some variants, the one or more processing circuits 1220 are furtherconfigured to report the information about the autonomous gap occurrenceseparately for gaps created in the uplink and downlink.

In some variants, the one or more processing circuits 1220 areconfigured to signal the information about the autonomous gap occurrencewhen reporting measurements, such as downlink signal quality, downlinksignal strength, physical cell identity or global cell identity etc.

In some variants, the one or more processing circuits 1220 areconfigured to signal the information about the autonomous gap occurrencewhen requested by the serving radio network node.

When using the word “comprise” or “comprising” it shall be interpretedas non-limiting, i.e. meaning “consist at least of”.

This disclosure refers interchangeably to acquiring system informationfrom a cell, or from a node (e.g. a NodeB or eNodeB). For completeness,it is pointed out that while the system information is transmitted froma physical node (e.g. NodeB or eNodeB), certain information, such as theCGI or E-CGI may be associated with a particular cell which is beingserved by that node. In particular, one base station may serve severalcells or cell sectors, in which case the base station may transmitdifferent system information in the various cells. Furthermore, a“neighboring base station” or “neighboring node” within the context ofthis disclosure should be understood as a base station or node whichserves a neighboring cell. Thus, the physical base station or node doesnot necessarily need to be located in close proximity to the measuringuser equipment.

The present invention is not limited to the above-describe preferredembodiments. Various alternatives, modifications and equivalents may beused. Therefore, the above embodiments should not be taken as limitingthe scope of the invention, which is defined by the appending claims.

In particular, it should be noted that the embodiments of the inventionin this disclosure apply to various scenarios such as forintra-frequency, inter-frequency, inter-RAT, e.g. when serving andtarget cells belong to E-UTRA FDD and TDD respectively or vice versa, orwhen serving and target cells belong to E-UTRA and UTRA respectively orvice versa. Furthermore, the embodiments described above apply to theUE, which is decoding system information such as the CGI of the targetcell, when it is in DRX state as well as in non DRX state. In addition,the invention applies when autonomous gaps are used by the UE to acquirethe system information of any type of target cell i.e. home basestation, pico base station or any base station in a heterogeneousnetwork environment. Also, the underlying aspects of the invention applywhen the UE is acquiring the CGI of the target cell for any otherpurpose such as for automatic neighbor relation as part of a selforganizing network (SON). Broadly, the principles of the invention applyto any case where a UE reads the system information of a neighbor cellor target cell for any purpose, and thereby creates gaps in the downlinkand/or uplink service with the serving node.

The invention claimed is:
 1. A method in a radio network node forscheduling data transmission or reception, the method comprising:predicting at least one autonomous gap occurrence in which userequipments served by the radio network node will use autonomouslycreated gaps for acquiring system information from a neighboring basestation and during which the user equipments are not able to receivedata from the radio network node or are not able to transmit data to theradio network node, wherein predicting the at least one autonomous gapoccurrence comprises determining when the neighboring base stationtransmits system information; and scheduling one or more of the userequipments for data transmission or reception in a time period that doesnot overlap with any predicted autonomous gap occurrence.
 2. The methodof claim 1, further comprising requesting one of the user equipments toread system information from the neighboring base station.
 3. The methodof claim 2, wherein the system information to be read comprises a CellGlobal Identifier (CGI) of the neighboring base station.
 4. The methodof claim 1, wherein determining when the neighboring base stationtransmits system information comprises determining timing informationfor the neighboring base station, the timing information comprising atleast one of frame start timing and the System Frame Number (SFN). 5.The method of claim 4, wherein the timing information is determinedbased on a measurement report received from a reporting one among theuser equipments, and wherein the measurement report relates to theneighboring base station.
 6. The method of claim 4, wherein the framestart timing and the SFN are determined based on a message received fromanother network node.
 7. The method of claim 4, wherein the timinginformation is determined by performing correlation over a pre-definedset of synchronization or pilot signals transmitted by the neighboringbase station.
 8. The method of claim 1, further comprising predictingthe duration or number of autonomous gap occurrences.
 9. The method ofclaim 8, wherein the duration or number of autonomous gap occurrences ispredicted based on the downlink signal strength or quality of theneighboring base station as indicated in a measurement report thatrelates to the neighboring base station and is received from a reportinguser equipment among the user equipments that are served by the radionetwork node.
 10. The method of claim 9, wherein the duration or numberof autonomous gap occurrences are predicted based on the receivercapability of the reporting user equipment.
 11. The method of claim 8,wherein the duration or number of autonomous gap occurrences arepredicted based on the time required by a reporting user equipment toidentify the physical layer identity of the neighboring base station,wherein the reporting user equipment is among the user equipments servedby the radio network node and sends a measurement report relating to theneighboring base station.
 12. The method of claim 8, wherein theduration or number of autonomous gap occurrences are predicted based onwhether the serving radio network node and the neighboring base stationoperate on the same or different carrier frequencies.
 13. The method ofclaim 1, wherein the duration or number of autonomous gap occurrencesare preconfigured.
 14. The method of claim 13, wherein the preconfiguredduration of the autonomous gap occurrences is between 2 and 4 subframes.15. The method of claim 13, wherein the number of autonomous gapoccurrences is preconfigured to be the maximum number of autonomous gapoccurrences possible within a measurement period.
 16. The method ofclaim 1, further comprising configuring a Discontinuous Reception (DRX)cycle of the one or more user equipments to be scheduled such that DRXON periods do not overlap with any predicted autonomous gap occurrence.17. The method of claim 16, wherein the same measurement period is usedfor acquiring the system information of the neighboring base stationregardless whether DRX is used or not and regardless of the length ofthe DRX cycle when DRX is used.
 18. A radio network node comprising oneor more processing circuits that are configured to: predict at least oneautonomous gap occurrence in which user equipments served by the radionetwork node will use autonomously created gaps for acquiring systeminformation from a neighboring base station and during which the userequipments are not able to receive data from the radio network node ortransmit data to the radio network node, wherein predicting the at leastone autonomous gap occurrence comprises determining when the neighboringbase station transmits system information; schedule one or more of theuser equipments for data transmission or reception in a time periodwhich does not overlap with any predicted autonomous gap occurrence.